Electronic devices, including portable electronic devices, have gained widespread use and may provide a variety of functions including, for example, telephonic, electronic messaging, and other personal information manager (PIM) application functions. Portable electronic devices include, for example, several types of mobile stations such as simple cellular telephones, smart telephones, wireless personal digital assistants (PDAs), and laptop computers with wireless 802.11 or Bluetooth capabilities.
Often these portable electronic devices include physical keyboards or keypads to input information. One benefit of a physical keypad is that it typically provides tactile feedback to a user. The tactile feedback from the keypad can be achieved in a variety of ways including the use of one or more collapsible dome switches associated with or corresponding to depressible keys of a keypad. To provide tactility, conventional keypads typically include a flexible or printed circuit board disposed between collapsible dome switches and a keypad support or tray (e.g., a housing).
Additionally, some keypads include a light source to illuminate the keys of the keypad to facilitate identification of the keys when using the portable electronic device in a dark environment with reduced visibility. A light guide film or panel is often used to deflect, reflect or channel light from a light source to illuminate the keypad. The light guide film is often placed over the dome switches. Thus, the light guide film typically has a convex or dome shape to accommodate for the shape or profile of the dome switches. For example, some conventional light guide films include a plurality of dome shaped surfaces to cover each dome switch of the keypad.
However, a dome shape light guide film provides a non-linear path through which light travels. In some instances, a non-linear light path due to the dome shape of the light guide film may cause light to be unevenly distributed, causing hotspots that receive too much light and dull spots that do not receive enough light to effectively illuminate the keypad. In some examples, the dome effect of the light guide film may cause light emitted from the light source to seep and erroneously highlight other keys of the keypad, thereby decreasing the effectiveness of the light guide film. Moreover, a light source having a greater intensity or luminance is often required due to the dome effect of the light guide film, thereby requiring more energy to power the light source. Further, the dome shaped light guide film significantly increases tactility restricting forces, thereby reducing the tactility of the keypad.